1. Field of the Invention
The present invention relates to a change-speed gear or transmission in group-type construction, especially for tractors, and comprises a main gear-shifting mechanism and an auxiliary or group gearing which is connected thereto. Gears are disposed on a main shaft and can be driven at a plurality of different speeds from a primary shaft, either via gears of an intermediate shaft, or by means of direct coupling of the primary and main shafts. For forward stages of the group gearing, the gears of the main shaft mesh with gears which are freely rotatably mounted on an output shaft and can be coupled therewith. For a reverse stage of the group gearing, a gear is provided which is freely rotatably mounted on the output shaft and can be coupled therewith.
2. Description of the Prior Art
With one known change-speed gear of the aforementioned general type (German Offenlegungsschrift No. 24 04 844), a reversing gear having two gears is disposed between a rigid gear of the main shaft and the gear which is rotatably mounted on the output shaft and serves for the reverse stage of the group gearing. Furthermore, gear shift sleeves for connecting altogether five gear or speed changes of the main gear-shifting mechanism are disposed together with the corresponding rotatably mounted gears partially on the main shaft and partially on the intermediate shaft. To drive a creep speed gear of this change-speed gear, a gear is provided which is rigidly connected with the main shaft; otherwise, this last gear has no function. All of these features of the heretofore known change-speed gear lead to an overall very complex and expensive construction, as well as to undesired large dimensions of the transmission. Arranging the gear shift sleeves partially on the intermediate shaft and partially on the main shaft is a drawback for the arrangement of the required gear-shifting mechanisms and during the assembly or disassembly of the intermediate shaft and the main shaft during manufacture or repair of the transmission.
It is an object of the present invention to eliminate these drawbacks and thereby to provide a change-speed gear in group-type construction which is as compact as possible and which can be manufactured from a small number of components, yet allows a large number of different gear ratio stages to be connected with as uniform a gradation as possible.